1. Field of the Invention
The present invention is directed to video adapters for use in personal computers and software for controlling the same. More particularly, the video adapter of the present invention includes at least two television tuners and sends video data to multiple computer displays.
2. Background
Video adapters (or "video cards") convert computer data to video signals for output to a monitor or similar output device. A typical Video Graphics Array ("VGA") card has its own memory and digital-to-analog converter ("DAC"), but does not actually process data, which is performed by the computer's CPU, including writing and reading of text, as well as drawing simple graphics primitives such as pixels, lines and memory transfers for images.
Programs such as DOS-based word processors run in VGA text mode while graphics-based programs like games run in graphics mode. The operating system sold under the trademark Windows 3.1 by Microsoft Corp. runs in VGA graphics mode as default, meaning that every pixel that is displayed as a part of the background, a window, or a text character must be written using basic VGA calls. The low-level nature of the VGA command set dictates that numerous commands be required to do something as simple as moving or closing a window. Clearly, an enormous amount of data is required to move from the VGA card, along the bus, into the CPU, and on into the card's memory, and vice-versa.
Accelerated video cards, however, have their own processor (or "accelerator"). Thus, an accelerated card may perform many video operations with only minimal input from the CPU. Indeed, the accelerated video card can perform all of the operations usually performed by the CPU with a VGA card. This frees the bus and the CPU to execute other tasks, and speeds-up video operation. Unlike VGA mode, where every pixel must be moved to and from the card via the bus and CPU, the accelerated card can perform the same operations with instructions consisting of only a few bytes being transferred along the bus. This results in an enormous performance gain for most common graphics operations, including bitmap and pixmap transfers and painting, movement of sprites and icons, opening and closing of windows, etc.
The increased performance of accelerated cards has permitted the introduction of more advanced graphics features. For instance, certain advanced accelerated cards now feature television tuning capabilities. Television cards include a television tuner capable of receiving and tuning a video source from a cable or a video cassette recorder. The card then converts the incoming video source into a signal that may be displayed on a conventional computer monitor. Cards with television tuners typically have additional processing and memory requirements.
Television-tuning video cards have numerous real-world applications. Medical personnel, for instance, may require video images together with computerized data during surgery. Seismic technology experts must locate, use, and analyze video tape of areas along fault lines or experiencing minor seismic activity. In the business arena, securities and commodities brokers rely upon several television and computer screens to advise their clients.
As more video data becomes necessary, the need for additional screens increases. The number of available screens, however, is limited by the number of available expansion slots within the computer. As more screens are needed, additional cards may be added. Most of today's computers include at least six expansion slots that may be used for additional monitors or for other peripherals. Additionally, under the current paradigm, each screen must typically be supported by its own CPU. This additional "footprint" requirement is an unwelcome encroachment on, for example, the desk or floor space of stockbrokers. It would be advantageous to support multiple displays from a single CPU.
Unfortunately, as a greater number of peripherals hit the market, the number of expansion slots appears to be dwindling. In other words, sound card manufacturers, zip drive makers, and CD-ROM drive makers are competing for the same finite number of expansion slots within each computer. Moreover, differing bus standards, such as PCI and ISA, further limit the number of expansion slots. Thus, a card having a PCI bus interface would be limited to the number of PCI bus expansion slots in the computer.
The addition of multiple graphics cards has the further disadvantage of requiring the user to control each screen independently. If two cards are provided by different manufacturers, the software utilities for each card may not be compatible. Even if two cards from the same manufacturer are used, there is no guarantee that the software required to run both cards will run seamlessly and without error. The user may become confused when faced with numerous video inputs and outputs to manage.